Fabrics woven from many synthetic fibers, and especially from polyester or blends comprising polyester and cotton fibers, are often very difficult to clean with conventional washing apparatus, e.g. washing machines. Polyester fibers are relatively easy to stain with oily (lipophilic) soils, but at the same time are difficult to wet in aqueous solution due to their hydrophobicity.
Textile manufacturers have addressed these problems by applying soil release finishes to these fabrics. These soil release finishes are most often hydrophilic in nature and can thus enhance the wetting of the fabrics by detergent solutions. This in turn helps to promote the rollup of oily soils during the wash cycle. The soil is removed from the fabric and transferred to the detergent. Thus, these surface coatings are known to impart soil release properties to fibers and fabrics so treated. The soil release finish can also act as a barrier between the surface of the fabric and the soil.
Soil release finishes can be applied to textiles in a variety of ways. In some cases, a non-permanent coating can be deposited in the rinse cycle of a conventional laundry process. In instances where a more permanent finish is required, the overlayer can be "heat set" to the fabric by drying at elevated temperatures often with mechanical pressure on the textile.
Often times, however, the surface coating and concomitant soil release capability is imparted to the fabric during a pretreatment process in which an aqueous bath is employed. The aqueous bath will often contain a pretreatment polymer with concentrations often ranging from 0.05-15% active. The pretreatment process basically comprises contacting the fabric surfaces with a dispersion of the polymer, drying the textile surface and then heat setting the finish using a device such as, for example, a hot clothes iron.
U.S. Pat. No. 4,999,869 describes soil release polymers made of polyalkylene oxide and vinyl esters which are used during the pretreatment process.
Likewise, U.S. Pat. No. 5,156,906 relates to the use of certain graft copolymers of polyethylene terephthalate/polyoxyethylene terephthalate with vinyl propionate and/or vinyl acetate as soil release agents for man-made fabrics, e.g. polyester blends.
Distinct from the concept of "soil release" is what is referred to as "anti-soil redeposition". The latter is a process which prevents the redeposition of soil which has already dissolved or dispersed in the wash water. It is obvious that the functions of the detergents and the surface finishing chemicals must complement each other in the anti-redeposition process. But although the anti-redeposition process is often confused with soil release, it is not the same thing. In fact, there is very little direct connection between the two. In this regard, see Bille et al., "Finishing for Durable Press and Soil Release", Textile Chemist and Colorist, vol. 1, No. 27 (1969).
Numerous polymers have been described as anti-redeposition agents. U.S. Pat. No. 4,746,456 describes anti-redeposition agents made of polyalkylene oxides and vinyl acetate. U.S. Pat. Nos. 4,846,994 and 4,846,995 are directed to soil anti-redeposition with polyalkylene oxide and vinyl esters.
U.S. Pat. No. 4,849,126 relates to soil anti-redeposition agents with polycondensates based on polyesters, polyester urethanes and polyester amides grafted with certain vinyl esters. For example, polyesters of terephthalic acid may be grafted with vinyl acetate. While disclosing the after-treatment of a fabric surface to impart anti-redeposition properties utilizing the graft polymers set forth therein, the '126 patent makes no reference of employing these polymers for the pretreatment of the fabric to impart soil release properties thereto.
There presently exists a need in the art for a method of pretreating fabric and textile surfaces with certain polymers of vinyl ethers so that important soil release properties may be imparted thereto. There also exists a need for textile material and fabrics, e.g. cotton and cotton/polyester blends, so treated.
Further, as ecological standards become more stringent, there is also a need for soil release polymers, which unlike some found in the literature today, are highly stable for extended periods of time in alkaline environments. These soil release compounds should not break down even in highly alkaline waters approaching a pH of about 14. But when these polymers are exposed to an environment that is slightly acidic, as can occur in surface water containing dissolved carbon dioxide, there is also the requirement that they be able to chemically degrade to their monomeric components. This feature will facilitate their overall biodegradation.